Since being found as a murine antisterility vitamin, tocopherol has been importantly used as a substance having pharmacological activities over a wide range not only in the field of medicines but also in the fields of foods, cosmetics, fisheries and livestock industry.
However tocopherol is a viscous, fat-soluble compound and unstable to oxygen, heat, light and alkalis, which restricts application thereof. Thus attempts have been made to solve these problems by using tocopherol in the form of derivatives which are stable to oxygen, for example, esters such as acetate and nicotinate. However, these esters are insoluble in water, similar to tocopherol.
It has been reported that 70 mg of .alpha.-tocopheryl phosphoacetate sodium salt can be dissolved in 1 ml of water (JP-B-45-21711, the term "JP-B" as used herein means an examined Japanese patent application. Characteristics of tocopherol phosphate ethylene glycol derivatives in relation to water are also described in Yakugaku Zasshi, 75 (11), 1322 (1955), and Chem. Pharm. Bull., 19 (4), 687 (1971). However, the former suffers from a disadvantage that the solution becomes turbid under neutral conditions, and the latter exhibits only a low water solubility of 0.02% in the form of diethylene glycol ester. In the latter case, a pentaethylene glycol ester shows a high water-solubility of 9.6%, but it is necessary to use a phosphorylating agent together, the synthesis of which is difficult and requires complicated procedures involving several steps.